1. DNA Questions What are nucleotides?
What are the four nitrogen containing bases on DNA?
What is a double helix? Sketch it.
What are the DNA base pairs?
What is DNA?
What type of biomolecule is DNA?
What is replication?
How might DNA relate to cancer?

2. The Big Ideas…Characteristics of Living Things
Made of Cells
Reproduce (sexually or asexually)
Have DNA (genetic information)
Grow & Develop
Need/Use Energy (metabolism)
Respond to Environment
Maintain Homeostasis (constant internal environment)
Change Over Time (evolve)
Form Systems & Have Systems (related parts)
Structure & Function are Related

3. 1953: The structure of the DNA molecule is first described.
As you can see from the model, the structure is basically a long, …twisted ladder type thing.
1953: The structure of the DNA molecule is first described.

4. KEY CONCEPT DNA structure is the same in all organisms.

5. The monomer for DNA is a nucleotide (Backbone & Bases)
Each nucleotide has three parts.
nitrogen-containing base
deoxyribose sugar
phosphate group
The base is the only part of a nucleotide that will change.
phosphate group
deoxyribose (sugar)
nitrogen-containing
base

6. The nitrogen bases are the only difference in the four nucleotides.

7. Those are the basic parts of DNA, but how did we figure out how it was put together?

8. Franklin’s x-ray images suggested that DNA was a double helix.
X-Ray Evidence
In the early 1950’s a British scientist named Rosalind Franklin began to study DNA.
Rosalind wanted to see what she was studying, so she took pictures of DNA with an X-ray.
Franklin’s x-ray images suggested that DNA was a double helix.
She does not receive much of the credit that she deserves for her research.
TED-Ed: Rosalind Franklin - DNA's Unsung Hero

9. Chargaff’s Rules
Erwin Chargaff was also studying the molecules present in DNA.
He realized that the frequency of Adenine bases equaled Thymine bases / Same for Cytosine and Guanine.
Number of A = Number of T
Number of G = Number of C

10. Nucleotides always pair in the same way.
The base-pairing rules show how nucleotides always pair up in DNA.
A pairs with T
C pairs with G C G T A

11. Watson and Crick determined the three-dimensional structure of DNA by building models.
They realized that DNA is a double helix that is made up of a sugar-phosphate backbone on the outside with bases on the inside.
100 Greatest Discoveries - DNA

12. Bonding - Backbone is covalent bonds (STRONG).
Bonding - Bases are hydrogen bonds (weak).
Hydrogen bond
Covalent bond
Sugar/Phosphate
Backbone
Nucleotide
(monomer)
Amoeba Sisters - DNA Structure
CC - DNA & Replication